Pressure transmission system comprising a device for identifying membrane ruptures and connection adapter comprising a device for identifying membrane ruptures

ABSTRACT

A pressure transmitter for transferring a pressure from a pressure prevailing in a first medium onto a second medium includes a pressure chamber between a platform and a dividing membrane, wherein the pressure chamber is fillable with the second medium and has a pressure chamber opening, through which the pressure can be transmitted by means of the second medium to a pressure measurement cell. The pressure transmitter includes a sensor for monitoring a material property of the second medium, preferably a conductivity sensor with at least one electrode, which sensor can detect contaminants in the second medium from the first medium following a rupture of the dividing membrane on the basis of changes in the monitored material property. The sensor is in flow connection with the pressure chamber by way of the pressure chamber opening.

[0001] The invention relates to a pressure transmitter, or mediator,with diaphragm seal, for transferring a pressure from a pressureprevailing in a first medium onto a second medium.

[0002] More exactly, the invention relates to pressure transmittershaving:

[0003] a platform;

[0004] a dividing, or separating, membrane, or diaphragm, which issecured at its edge onto the platform, wherein a first surface of thedividing membrane, facing away from the platform, can be brought intocontact with the first medium, and a second surface of the dividingmembrane, facing toward the platform, forms with the platform a pressurechamber, which can be filled with the second medium, wherein thepressure chamber has a pressure chamber opening, through which thepressure can be transferred by means of the second medium; and

[0005] a sensor for monitoring a property of a medium contained in thechamber.

[0006] Devices of this type are, in addition to other uses, used forpressure measurement in aggressive media. The dividing membrane iscontacted with an aggressive first medium and the pressure prevailing inthe first medium is transferred to a second medium in the pressurechamber. There, the pressure is conducted over a suitable pressureconducting line to a pressure measurement cell. Pressure transfer usinga pressure transmitter and an attached pressure line can, however, alsobe desired in the case of non-aggressive media, for bridging largedistances between the first medium and the location of the pressuremeasurement cell.

[0007] Incompressible oils are preferably used as the second medium forpressure transmission. In so far as such a substance is suited forcontaminating a medium being measured, and for various other reasons, itis necessary to recognize early that there is a leak in the dividingmembrane, or a rupture of the dividing membrane. To this end, Bastiaandiscloses in the European patent application EP 0 838 672 a pressuretransmitter, in which the pressure chamber has in its wall a dead-endhole, in which the electrode of a conductivity sensor is arranged. Insuch case, when the dividing membrane breaks, the first medium diffusesinto the pressure chamber and into the dead-end hole, whereupon a changein the conductivity is detectable, provided that the first medium has aconductivity which deviates significantly from that of the secondmedium. This is especially the case, when the first medium is acorrosive medium and the second medium is an oil.

[0008] For the various pressure measurement applications, there is animmense number of pressure transmitters, which are fitted to thedifferent demands of the applications. A very high manufacturing cost isrequired to equip this multiplicity of sensors with the conductivityprobe proposed by Bastiaan. Additionally, the arrangement of Bastiaanneeds a minimum diameter of 1.5 inches, or 3.8 cm, for placing theconductivity sensor next to the pressure conducting line, as followsfrom the applicant's product description “Badoterm's MDS DiaphragmLeakage Detection System” for a product corresponding to the subjectmatter of the application. Such a constraint is unacceptable for manyapplications.

[0009] Moreover, transport of the contaminants to the sensor happenspurely diffusively in the described pressure transmitter. This can leadto a large time delay between the occurrence of a leak and the detectionof the contamination resulting therefrom, depending on the depth of thedead-end hole and the particulars of the installation of the pressuretransmitter.

[0010] It is, consequently, an object of the present invention toprovide an improved pressure transmitter, which overcomes thedisadvantages of the prior art.

[0011] The object of the invention is solved by the devices of theindependent claims 1 and 10. Additional advantages and aspects of theinvention follow from the dependent claims, the description and thedrawings.

[0012] The pressure transmitter of the invention for transfer of apressure from a pressure prevailing in a first medium onto a secondmedium comprises

[0013] a platform;

[0014] a dividing membrane, which is secured at its edge onto theplatform, wherein a first surface of the dividing membrane, facing awayfrom the platform, can be brought into contact with the first medium,and a second surface of the dividing membrane, facing the platform,forms with the platform a pressure chamber, which can be filled with thesecond medium, wherein the pressure chamber has a pressure chamberopening, through which the pressure can be transmitted by means of thesecond medium; and

[0015] a sensor for monitoring a material property of the second medium,wherein

[0016] the sensor is in flow connection with the pressure chamber by wayof the pressure chamber opening.

[0017] Preferably, the sensor is a conductivity sensory. Additionally,the sensor can be a capacitive sensor, which monitors the relativedielectric constant of the second medium.

[0018] Following the occurrence of a leak in the dividing membrane, thematerial properties of the second medium are changed by contaminantsfrom the first medium. In so far as the contaminants spread, at least atconstant temperature and constant pressure, essentially diffusively, thesensor should preferably be spaced at a maximum so far from the dividingmembrane, that the expected diffusion time of the contaminants from aleak in the membrane to the sensor does not exceed a given time span.Depending on requirement, which essentially is determined by the contextin which the sensor is being applied, this time span can be in the rangeof minutes, hours, days or weeks. In order to be able to apply thepressure transmitter of the invention as universally as possible, thesensor element should be arranged with the smallest possible separationfrom the dividing membrane.

[0019] When the sensor is a conductivity sensor, it includes at leasttwo mutually separated electrodes, and the space between the electrodesis filled, at least partially, with the second medium. The sensor can,for example, exhibit a first and a second electrode, which are eachelectrically insulated from one another and from the platform orpressure supply line, as the case may be, or the sensor can exhibit afirst electrode, which is insulated from the platform or the pressuresupply line, as the case may be, and the platform or supply line servesas the counter electrode. A capacitive sensor can exhibit the samearrangement of the electrodes as a conductivity sensor.

[0020] In a preferred embodiment, the platform of the pressuretransmitter includes a line connection for connecting a pressureconducting, or supply, line, transmitting the pressure to a pressuretransducer. The pressure chamber opening opens into this lineconnection. The sensor can now, for example, be arranged in the lineconnection or in a connection adapter with which the pressure conductingline is attached at the line connection.

[0021] The connection adapter includes a pressure transmitterconnection, which is complementary to that of the line connection, and apressure line receiver. The connection adapter includes, additionally, afirst electrode and a second electrode of the sensor. The pressure linereceiver can, for example, have a chamber in the connection adapter,into which chamber the pressure conducting line opens. The firstelectrode and the second electrode can, for example, be secured in anopening of the chamber by means of a glass bushing. Particularlypreferred is an embodiment where the pressure conducting line islikewise secured by means of a glass bushing, especially the same glassbushing.

[0022] The arrangement of the sensor for monitoring a material propertyof the transfer medium in the pressure chamber opening or in anothersection communicating with the pressure chamber by way of the pressurechamber opening has, additionally, the advantage that it leads also to atransport of the contaminants by convection, or flow, of the transfermedium.

[0023] This should frequently cause a faster detectability of thecontaminants than the purely diffusive transport in the arrangement ofBastiaan. Assuming, for example, a pressure chamber working volume of100 mm³ and an opening diameter of 1 mm, then this means during anoverload pressure pulse a displacement of the total working volume inthe opening by about 127 mm. In this way, the contaminants can reach thesensor with the transfer medium considerably faster than is the casewith the arrangement of Bastiaan.

[0024] Equally, temperature fluctuations can lead to a convectivetransport of the contaminants. A temperature change in the pressureconducting line of, for example, 10° C. leads, in the case of a volumeexpansion coefficient of about 10⁻³/K, a pressure conducting line lengthof 10 m and an internal diameter of 1 mm, to a volume change of about 80mm³, which corresponds to a movement of the liquid column of about 100mm at the end of the pressure conducting line. The described convectivetransport to the sensor is more effective, the longer the length of thepressure conducting line in comparison to the separation of the sensorfrom the dividing membrane.

[0025] For optimum utilization of this effect, the elements of thesensor, for example the electrodes of a conductivity sensor, should bearranged, as much as possible, in, or immediately bordering, an area ofthe pressure chamber opening, the pressure conducting line, or aconnection adapter between the pressure transmitter and the pressureconducting line, where the described convection flow flows through.

[0026] The invention will now be explained in more detail on the basisof the drawings, which show as follows:

[0027]FIG. 1: A perspective, cross-sectional drawing of a preferredembodiment of a pressure transmitter of the invention; and

[0028]FIG. 2: A preferred embodiment of a connection adapter of theinvention.

[0029] The pressure transmitter shown in FIG. 1 includes a platform 1,which has a preferably essentially cylindrically symmetric construction.Dividing membrane 2 is secured at its edge 21 onto the front side 13 ofthe platform, so that a pressure chamber 11 is formed between thedividing membrane 2 and the platform. The front side 13 of the platform1 can be provided in usual manner with a membrane bed, against which thedividing membrane 2 is pressed in the case of overload.

[0030] The pressure chamber 11 has an opening 12 for transmission of thepressure prevailing in the pressure chamber. The opening 12 ispreferably constructed as a capillary line. Opening 12 extends in thepreferred embodiment to a pressure line connection 14, which preferablyis in the form of an essentially cylindrical, or axially symmetric,recess on the side of the platform 1 opposite to that containingdividing membrane 2.

[0031] The connection of the pressure conducing line 4 occurs, in apreferred embodiment, by means of a connection adapter 3, in which thesensor for monitoring a material property is integrated. Details of theconnection adapter 3 will now be described on the basis of referencealso to FIG. 2. The proportions of individual elements of the embodimentof a connection adapter shown in FIG. 2 differ from those of theembodiment of the connection adapter in FIG. 1. In both drawings,however, identical reference characters are used for correspondingelements.

[0032] The connection adapter 3 includes a pressure transmitterconnection 37 complementary to the line connection 14 and a pressureline receiver, which is formed in a preferably cylindrical, firstsection 33. The connection adapter 3 includes, additionally, a firstelectrode 31 and a second electrode 32 of the sensor.

[0033] The pressure transmitter connection 37 can, for example, includean essentially cylindrical, or conical, projection, which extends in theaxial direction from an end surface of the first section 33 and containsa canal 36, through which a flow connection is created between thepressure chamber opening 12 of the pressure transmitter 1 and thepressure line receiver.

[0034] In so far as the cylindrical projection has a smaller radius thanthe first section 33, the end surface of the first section outside ofthe cylindrical projection acts as an axial abutment surface, whichdefines the position of the connection adapter 3 with reference to theplatform 1 and, at the same time, effects a (perhaps supplemental) sealbetween the platform 1 and the connection adapter 3.

[0035] The lateral surface 38 of the essentially cylindrical projectioncan also, if required, be provided with an outer screw threadcomplementary to an internal thread in the wall of the pressure lineconnection 14.

[0036] The pressure line receiver can, for example, have a chamber 35 inthe connection adapter 3, and the pressure conducting line 4 is placedwith its inlet in this chamber 35. The sensor for monitoring a materialproperty of the second medium, here the electrical conductivity, is,likewise, arranged in the pressure line receiver. The first electrode 31and the second electrode 32 of the sensor can, for example, be securedin an opening of the chamber 35 by means of a glass bushing 34.Preferably, the pressure conducting line is likewise secured by means ofa glass bushing, wherein especially the same glass bushing 34 can beused. Equally, it is possible to secure the two electrodes, or thepressure conducting line, as the case may be, each in a separate openingby means of a glass bushing or another suitable means of securement.

[0037] The chamber 35 should, on the one hand, be sufficiently largethat the electrodes can be positioned insulated from one another andthat a suitable space filled with the second medium, or a transferfluid, as the case may be, extends between the electrodes. Moreover, thetransport of contaminants in the vicinity of the electrodes should occuras fast as possible. Therefore, paths as short and direct as possible,with large cross sections, should exist between the canal 36 in thepressure transmitter connection 37 and the electrodes. In so far as thecanal 36 is likewise a section of the path of contaminants, the canal 36should also exhibit as low a diffusion resistance as possible. On theother hand, the total volume of the transfer liquid in the system is tobe kept as small as possible, in order to minimize the influence oftemperature fluctuations on the total system.

[0038] Instead of two separate electrodes, it is also possible toprovide only one electrode and to measure the conductivity between thisone electrode and the platform, or the chamber.

[0039] Pressure conducting line 4 is preferably constructed as acapillary line. In the embodiment of the drawing, the capillary line istubular; it can, however, be a bore in a massive block, for example in adividing body, in which the sensor and the pressure connection adapteror a pressure transmitter connection can be integrated.

[0040] The pressure conducting line transmits the pressure present inthe second medium to a pressure measurement cell (not shown in furtherdetail), which produces a pressure-dependent, electrical signal.

[0041] The electrodes 31, 32 of the conductivity sensor are connected toa suitable evaluation circuit, which monitors the conductivity of thetransfer medium. The monitoring can, for example, occur continuously,periodically, or be event-controlled, for example by querying by amicroprocessor.

[0042] Even though, at the moment, conductivity sensors are preferredsensors for monitoring a material property of the transfer medium, thepressure transmitters of the invention can, fundamentally, utilize othersensors also. Suited additionally are, among others, capacitive sensors,pH-sensors, photometer or specific adsorption sensors, which detect thepresence of a chosen foreign substance from the first medium, or theprocess medium, in the transfer medium.

1-10. (Canceled)
 11. A device for transfer of a pressure from a pressureprevailing in a first medium onto a second medium, comprising: aplatform; a dividing membrane, which is secured at its edge on saidplatform, wherein a first surface of said diving membrane, facing awayfrom said platform, can be brought into contact with the first medium,and a second surface of said dividing membrane, facing toward saidplatform, forms with the platform a pressure chamber, which can befilled with the second medium, said pressure chamber has a pressurechamber opening, through which the pressure can be transmitted by meansof the second medium; and a sensor for monitoring a material property ofthe second medium, wherein: said sensor is in flow connection with saidpressure chamber by way of said pressure chamber opening.
 12. The deviceas claimed in claim 11, wherein: said sensor is a conductivity sensor.13. The device as claimed in claim 12, wherein: said conductivity sensorhas a first electrode and a second electrode, which are insulated fromone another and from said platform.
 14. The device as claimed in claim12, wherein: said conductivity sensor has an electrode, which isarranged insulated from said platform, in order to measure theconductivity of the second medium between said electrode and saidplatform or components conductively connected with said platform. 15.The device as claimed in claim 11, further comprising: a pressureconducting line, which is in flow connection with said pressure chamberopening.
 16. The device as claimed in claim 15, wherein: said pressureconducting line is a capillary line.
 17. The device as claimed in claim15, further comprising: a connection adapter, which connects saidpressure conducting line with said pressure chamber opening.
 18. Thedevice as claimed in claim 15, wherein: said connection adapter includessaid sensor.
 19. The device as claimed in claim 11, wherein: a variablepressure loading of said dividing membrane and/or a volume change of thesecond medium due to temperature fluctuations within a given workingrange of the device leads to a flow of the second medium through saidpressure chamber opening; said sensor is arranged at such a distancefrom said pressure chamber that at least a part of the medium containedin said pressure chamber at 50% of the nominal pressure and at theaverage temperature of the nominal temperature range of the device flowsto the position of said sensor at a compression of said pressure chamberof not more than 30%, preferably not more than 20%, especiallypreferably not more than 10%.
 20. A connection adapter for connecting apressure line with a pressure transmitter for transfer of a pressurefrom a pressure prevailing in a first medium onto a second medium, thepressure transmitter having a platform and a dividing membrane, which issecured at its edge on the platform, wherein a first surface of thedividing membrane, facing away from the platform, can be brought intocontact with the first medium, and a second surface of the dividingmembrane, facing toward the platform, forms with the platform a pressurechamber, which can be filled with the second medium; and wherein theconnection adapter comprises: a pressure line receiving a pressuretransmitter connection for producing a flow connection between thepressure chamber and the pressure line by way of the pressure chamberopening; and a sensor for monitoring a material property of the secondmedium, wherein said sensor is arranged such that it is in flowconnection with the pressure chamber through the pressure chamberopening following the connection of the pressure transmitter at saidconnection adapter.